The present invention relates generally to semiconductor devices and methods of preparation of such devices and, in particular, to miniaturized semiconductor devices prepared by self-alignment processes.
Prior art semiconductor devices, particularly, semiconductor memory devices having capacitors are generally formed by processes that include the steps of formulation of an element isolating region, formation of a capacitor region by forming a groove or by a layering process and then formation of a gate electrode and contact hole.
Reference is made to FIG. 6 wherein a prior art semiconductor device is shown. First element isolating oxide film 602 is formed in silicon substrate 601 by a known technique. Stopper region 603 is formed simultaneously. Gate oxide film 604 is formed on substrate 601 and gate electrode 605 is formed of polysilicon on gate oxide film 604. Low density diffused region 607 is formed in silicon substrate 601 using gate electrode 605 as a mask. Sidewall oxide film 608 is formed along the edges of gate electrode 605. Titanium is applied to the through surface of the device to form electrode portion 606 on gate electrode 605 and diffused region 609 on low density diffused region 607. Accordingly, electrode portion 606 and diffused regions 609 are formed as TiSi.sub.2 by a self-aligning process. An impurity is diffused by ion implantation and interlayer insulating film 611 is formed on the device. The device is annealed to form the source and drain diffused regions 610 under the TiSi.sub.2. A contact hole is formed by contact etching and an aluminum alloy connector 612 is deposited in the contact hole.
In the process described, it is necessary to arrange each of the elements such as capacitors, element isolating regions, gate electrodes and contact holes while allowing room for alignment of the gate electrode with each of the capacitor, the element isolating regions, the gate electrodes and the contact holes. The necessity of providing alignment space prevents the device from being miniaturized.
Furthermore, when the field insulating film of prior art semiconductor devices is formed by selective oxidation of the substrate (also known as "local oxidation of silicon" or "LOCOS"), it is necessary to form an anti-oxidation mask on the portion of the substrate where oxidation is not desired. The anti-oxidation mask is removed after forming the field insulating film, but the end portion of the film generally protrudes undesirably. This undesirable projection is known as a "bird's beak" and causes defects including disconnection of connectors formed in later process steps.
It is, therefore, desirable to provide a method for making a semi-conductor device that does not require alignment space to be maintained between the elements, thereby allowing the device to be miniaturized.